Coupling the optical energy of high energy sources of light such as lasers into optical fibers has become increasingly useful in commercial, industrial and military applications. Such coupling allows high optical energy to be readily redirected by optical fiber to where it is needed for its intended usage, whether that is communications, industrial cutting or welding, material processing, or remote destruction of enemy targets. When high optical energy is flexibly guided via optical fiber, it also allows for the combination of multiple sources that may be difficult to combine by other methods.
Optical fiber generally is comprised of a central core, a cladding layer surrounding the core, and often a buffer layer that surrounds and protects the cladding. When light is properly coupled into optical fiber it is directed into the core, which is designed to contain and guide the light along the length of the fiber. However, coupling from high energy sources of light is rarely perfect and some optical energy may stray into the cladding and sometimes into the buffer layer as well. Such stray optical energy, particularly from high energy sources, can cause heating of the optical fiber and other couplings or devices, and can cause significant damage or destruction of the fiber, the couplings or other devices.
In arrangements where there is no buffer layer present at the entrance to the optical fiber but rather is present further down the fiber's length, the stray energy that gets coupled into the cladding will scatter into the buffer layer and may cause damage further along the optical fiber.